Method for producing so-called porous metals.



UNITED. STAT METHOD FOR PRODUCING SO-CALLED POROUS METALS.

No Drawing.

Specification of Letters Patent. Application filed December 2, 1911. Serial 1V0. 663,592.

Patented Oct. 22, 1912.

T all whom it may concern:

Be it known that I, HARALD IMMANUEL HANNOVER, a subject of the King of Denmark, residing at Copenhagen, Denmark, have invented certain new and useful Improvements in a Method for Producing S0- Called Porous Metals, of which the following is a full, clear, and exact description.

This invention has for its object to provide a process for the production-of metals and alloys in a condition in which they have a very great number of fine pores. Such metals and alloys are hereinafter included in the term porous metals The process is carried out as follows For the producing of these porous metals alloys are used in which the less fusible particles become solid during the solidification of the alloy before the other more easily fusible particles, especially eutectic alloys,

solidify. When an alloy of this kind is heated to somewhat above the melting point of the more easily fusible parts, especially the melting-point of a eutectic alloy, these parts and especially a eutectic alloy, can be driven out of the rest of the mass by being either blown out, sucked out, forced out'by liquid pressure, or driven out by means of centrifugal force,-shock, or vibration. In order for instance to blow out a eutectic alloy from an alloy, the same can be cast so as to form a tube or part of a tube or be placed as the bottom in a tube, and when the tube has been heated, the blowing out of the eutectic alloy can be elfected by admitting a suitable gas or liquid such as carbonic acid under pressure into the tube. For instance the eutectic alloy may be blown out of a heated alloy of lead and antimony, richer in lead than the eutectic alloy of antimony and lead, by means of carbonic acid having an absolute pressure of about 2 atmospheres. The use of carbonic acid is preferred because as this substance is neutral to the heated metals and alloys. However, it has been found most practical to drive out the more easily fusible parts by centrifugal force and especially the eutectic alloy of plates composed for instance of cast antimony and lead and containing more lead than the eutectic alloy. After the driving-out operation a porous metal is obtained consisting substantially of .lead, which may be used for electrlc storage battery plates, filtering-plates, etc;, slnce-lt presents an exceedingly large contact surface for the acid in the battery,

whereby a storage battery of hitherto unknown large capacity and small weight may be produced. The pores of the porous metals may be filled with other substances in various ways. Oil may for instance be absorbed by these porous metals, or molten resin may be forced into the same. Bearings supplied with oil through the pores of the bearing-metal can thus be produced. When the porous metals are to be used for electric storage battery plates,the pores may be filled with powdered filling substance whichis introduced suspended in a liquid or carried in by an air-current blowing on the plate, or sucked through the plate. The filling substance may also be chemically precipitated in the pores.

By this process for the production of porous metals by the removal of easily fusible alloys, especially eutectic alloys from alloys which are heated above the melting-point of the easily fusible alloy, a completely new class of substances may be produced, the pores of which may remain empty or be filled with other substances.

In the carrying out of the preferred form of the improved process for the production of electricstorage battery plates by subjecting the metal-plates to centrifugal action in a room in which the air is heated, or in a warm liquid, a practical difliculty had to be overcome. The metal plates were not placed radially because this proved not to be so practical, butwere placed at right angles to a radius. Each plate was placed in a mold, the outside part of which was formed by wire-gauze through which the easily fusible parts could be driven out by the centrifugal force, the gauze being supported on the outside by a grating of metal bars. The centrifugal force, however, caused the oocurrence of stresses in the plates, so that sides of the mold must be pressed against the plateduring the process. For instance one or more swing weights swung out by the centrifugal operation action may by means of suitable connection organs be caused to press the sides of the mold inward with a slight pressure. The rotation of the apparatus may also be stopped for some moments and by means of a tightening mechanism one or more of theasides of the mold may receive a slight inward motion toward the metal plate or this can be the case during the rotation. come the difliculty above referred to.

As is well known'an electric storage battery plate. has a tendency to bend during the charging and discharging of the battery. This tendency may be removed by reversing the plates so that the side of the plate, which was facing outward during the centrifugal operation and became impressed by the wiregauze, is now turned inward and continuing the centrifugal operation for some time longer. It has also proved possible to rend off the outermost surface of the plateor .to shave it off in the still warm condition.

With a view of increasing their strength, the electric storagebattery plates might be produced in such a manner. that they partly consist of solid material in the shape of a frame, askeleton, etc., partly of pore-metal.

This may be effected in various ways. For I instance a battery plate consisting of an alloy of lead and antimony which hasbeen converted into a porous metal maybe soldered to a frame of solid lead. Besides using this obvious method more special methods can be used, of which the following may serve as examples.

Part of the gauze through which the easily fusible parts flow out may be covered with plate-strips which prevent the flowing out at the parts in question. For instance the gauze may be covered along its edges so as to provide the porous metal with a solid frame, or a few strips extending from the places, where the currents are leo. in, may be covered in order to prevent a too strong current from locally attacking a battery plate. Further, provision ma be made to prevent theeasily fusible particles from being removed from the interior of the plate, so that a solid core is left in the plate.

This is most easily done by means of vibra-- tions, whereby the easily fusible parts are caused to flow out of the superficial portions of the plate, the inner portions of the plate being left unaffected.

A frame or a skeleton of pure lead may be placed in the mold in which the/alloy of lead and antimony is cast and on to this skeleton the antimony alloy is cast, which will not become porous when the lead-antimony metal is converted into porous metaL' The improved process allows ofcasting electric storage battery platesinrather thick blocks, which are thereafter by sawing divided 'in plates.

The methods hereinbefore described are; only to beconsidered as given b *way of examples, and various details may altered without departing from the ,nature of the?- lnventiong thus a number of plates may be produced at a time; the tem erature may con'venlently be kept at the through electrical heating, etc.

Such expedients have over-.

the same into the shape desired, then heatbod esired heightv while leaving the fluid metal in the deeper-0 When a porous metal produced by an alloy of lead and antimony has been obtained according to this invention porous metals or alloys with a higher melting-point can be produced by precipitating the same galvanically in the pores of the porous metal and treating the formed body as if it were an alloy viz. by heating the same until the origihal orous metal is melted, and then driving it out by any suitable means such as centrifugal action. Porous metal of silver produced in this manner may be enameled by applying dif-. ferently colored enamel pastesby means of a hair-pencihso that they are absorbed in the pores, and afterward burning them in.- Porous metals produced according to this. invention may be used for filtering purposes.

Having now described and ascertained my said invention and in what manner same 35 is to be performedfl declare that what I' claim and desire to secure by U. S. A. Let ters Patent is:

1'. The process of roducing orous metal which consists in malt-ing an al oy of twoor more metals, then heating the 9.110 until lighter fusible segregations, especial y consisting rof a eutectic alloy, become fluid, while the rest of the 9.110 remains solid and finally mechanically orcing the'fluid particles outof the body of solid metal.

2.. The process of producing porous metal in a given shape which consists in making an alloy of two or more metals and forming ing the body" until lighter fusible segregations, especially consisting of a eutectic alloy, become fluid, while the rest of the body remains solid, and finally mechanically forcing the fluid particles out of the of solid metal, substantially 'as d e' O scri ed. a

3. The process of makingmetallic articles which are porous in certain parts only which consists in forming the articles of an alloy of two or more metals then covering 7 the surface of such parts 0 the article as are to remain non-porous with shielding strips, then applying heat to the article until lighter fusible segregations, especially consisting of a eutectic alloy, become fluid, whilethe rest of the article remains solid and finally mechanically forcing the" fl particles out of the uncovered parts of thearticle as described.

4. The process of making metal articles which consists in forming the same of-an alloy of two or more metals, then applying heat thereto until lighter fusible segregations, especially consisting of a eutectic alloy, become fluid, while the rest'iof the article remains solid, then mechanically re-- nioving the fluid particles from the surface of the article and to any desired depth,

portions undisturbed, whereby the articles Will have a porous surface, as set forth.

5. The process of making metallic articles which are porous locally, consisting in making parts of the article of a pure metal While other parts are made of an alloy of two or more metals, applying heat until fusible segregations, especially consisting of a eutectic alloy, become fluid, While the pure metal and the rest of the alloy remains solid and then mechanically forcing the fluid particles out of the articles, as set forth.

6. The process of producing porous metallic bodies consisting in forming the same of an alloy of two or more metals, applying heat until-lighter fusible segregations, espezially consisting of a eutectic alloy, become fluid, While the rest remains solid, then subjecting the body to centrifugal action While its surface is pressed upon by Walls Which prevent the formation of fissures in the said body.

7. In the process of producing porous metallic bodies, first making a porous metal or alloy body, then galvanically precipitating a metal or alloy of higher fusing point into the pores of the porous body, then applying heat until the metal or alloy of lower fusing point is liquid and finally removing said liquid metal from the body as described.

In Witness whereof, I have subscribed my signature in the presence of tWo Witnesses.

HARALD IMMANUEL HAN NOVER.

Witnesses V F. PETERSEN, W. SLETTING. 

